Update DMARC-how-to.md

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@ -23,10 +23,8 @@ DMARC addresses this problem and enables the owner of a domain to take explicit
* When using office 365, the forwarding of calendar appointments from a DMARC projected domain fails. This is a known issue. Read more on the [Office 365 UserVoice forum](https://office365.uservoice.com/forums/264636-general/suggestions/34012756-forwarding-of-calendar-appointments-from-a-dmarc-p) and don't forget to submit your vote!
* There is a workaround: Forward the appointment as an "iCalendar file" or as an attachment.
# Creating a DMARC record
The DMARC policy is published by means of a DNS TXT record. Before setting up a DMARC record, lets first take a look at all the configuration tags that can be configured within a DMARC record.
## Overview of DMARC configuration tag
# Overview of DMARC configuration tags
The DMARC policy is published by means of a DNS TXT record. A DMARC record can contain several configuration tags. The table below will list all configuration tags and explain their purpose.
| DMARC configuration tag | Required? | Value(s) | Explanation |
| --- | --- | --- | --- |
@ -44,11 +42,6 @@ The DMARC policy is published by means of a DNS TXT record. Before setting up a
Be aware that implementing a DMARC record without a rua configuration is possible, this is not advised because the DMARC XML files that are received by implementing a rua email address can help with implementing DKIM or SPF to meet the DMARC requirements.
## Setting up a DMARC record
Depending on your preferences and needs, you can determine the value of the configuration tags. The values below seem like a good starting point when setting up
_dmarc IN TXT "v=DMARC1; p=quarantine; rua=mailto:dmarc@example.nl; ruf=mailto:dmarc@example.nl; fo=0; adkim=r; aspf=r; pct=100; rf=afrf; ri=86400; sp=quarantine"
# Implementing DMARC with OpenDMARC for Postfix with SpamAssassin
**Specifics for this setup**
* Linux Debian 9.8 (Stretch)
@ -64,6 +57,13 @@ Depending on your preferences and needs, you can determine the value of the conf
## Outbound e-mail traffic
DMARC for outbound e-mail traffic can be accomplished by publishing a DMARC policy as a TXT record in a domain name's DNS zone.
### Setting up a DMARC record
Depending on your preferences and needs, you can determine the value of the configuration tags. The values below seem like a good starting point when setting up DMARC.
_dmarc IN TXT "v=DMARC1; p=quarantine; rua=mailto:dmarc@example.nl; ruf=mailto:dmarc@example.nl; fo=0; adkim=r; aspf=r; pct=100; rf=afrf; ri=86400; sp=quarantine"
Because this specific setup uses SpamAssassin for classifying e-mail to be SPAM or legitimate (HAM), the DMARC policy used is quarantine. This is done to prevent OpenDMARC from blocking the e-mail and, as a result, not enabling SpamAssassin to do its job.
## Inbound e-mail traffic
DMARC for inbound e-mail traffic can be accomplished by setting up OpenDMARC and integrate it with Postfix.